The proposed studies will expand upon my preliminary work on neuronal RNA quantitation in the human brain by applying similar RNA analysis to the brain of rhesus monkeys ranging from 3 to 30 years of age. Furthermore, complex dendritic branching patterns and synaptic profiles will be studied by using the Golgi-Cox and rapid Golgi methods for light microscopy and the ethanolic phosphotungstic acid staining method for electron microscopy. Morphometric measurement of these neuronal parameters will be obtained with the use of the computerized graphic digitizer. The studies will then examine the possibility that changes in neuronal RNA content, dendritic ramification and synaptic profile may reflect aging changes in the rhesus monkey brain. These data obtained on the rhesus monkey will be important in relating present knowledge of the aging brain in other species to the aging human brain.